1. Field of the Invention
The present invention relates to a process for improving low quality coal. More particularly, the present invention relates to a process for the production of improved coal from low quality coal, such as brown coal and lignite, which comprises efficiently dehydrating the low quality coal and making it hydrophobic without consuming a large quantity of energy.
2. Description of the Prior Art
In general, low quality coal, such as brown coal, lignite, etc. is not suitable for transportation and handling since, although it has certain properties required for fuel, its water content is high, and it is liable to cause spontaneous combustion when it is dried. Therefore, such low quality coal is used only in and around the areas where it is produced.
A number of methods have been proposed to improve low quality coal by dehydration, including (1) an evaporation process, (2) a mechanical dehydration process, and (3) a nonevaporation type dehydration process. These methods, however, suffer from various disadvantages: for example, the process (1) consumes a large quantity of energy, which is not desirable from an economic viewpoint; the process (2) can remove water only up to about 30%; and the process (3) needs large-sized equipment, which is also not desirable from an economic standpoint.